Estrogenic and antiproliferative properties of soy sapogenols in human breast cancer cells in vitro

Two soy sapogenols, soyasapogenol A (SA) and soyasapogenol B (SB) were tested for their estrogenic activities in estrogen responsive MCF-7 or estrogen-insensitive MDA-MB-231 (MDA) human breast cancer cells. SB and SA had differential actives on cell proliferation with 10 μ m SB being growth inhibitory to MDA cells with no significant effect at any concentration on MCF-7 cells. SA also inhibited MDA cell proliferation at 10 μ m, but at this same dose stimulated a 2.5-fold increase in MCF-7 proliferation. SA (0.1–10 μ m) induced pS2 mRNA levels and the induction was blocked by co-treatment of cells with the anti-estrogen ICI 182,780. SA also induced the formation of an ER–ERE DNA complex measured by electrophoretic mobility shift assay. In summary, these results show that soyasapogenol A is estrogenic, whereas soyasapogenol B is growth inhibitory.